In a teaching playback type robot, the registration of predetermined positions and input/output control commands of operations of operation jigs is implemented by operating the robot by operating a portable teaching unit (also referred to as a pendant) in a teaching mode of the robot using an operation procedure carried out by the robot as an operation program.
Since this teaching unit is controlled by an operator who holds it, weight and size reductions have been taken into consideration. However, to receive a power supply from the robot controlling unit and transmit and receive signals, the teaching unit has been connected by a composite cable in which a power supply line and a signal line are combined.
However, when the operator registers a position of the robot in the vicinity of the robot, the cable of the teaching unit gets entangled with equipment lying on the periphery of the robot or the cable is too short to reach a desired position, whereby there is sometimes caused a problem with teaching the robot, this having given rise to a strong demand for eliminating the cable. As a measure to deal with this demand, there has been proposed an idea of using wireless connection for transmission and reception of signals (refer, for example, to JP-A-58-151608). A power supply to a teaching unit is configured to be implemented by a battery that the teaching unit possesses, and to charge the battery, there have been proposed various ideas which have now been implemented on cordless telephones and portable wireless telephones, for example.
A conventional robot system will be described using a block diagram shown in FIG. 5.
In the figure, a robot 101 is connected to a robot controlling unit 102, and a teaching unit 103 is also connected to the robot controlling unit 102. The robot 101 is surrounded by a safety protective fence 104 so as to prevent an erroneous access to an operational range of the robot 101 by an operator working on the periphery of the robot 101 in operation, and an open-close detection unit 106 for detecting an open-close of a safety protective fence door 105 is mounted at an exit/entrance in the safety protective fence 104, an open-close signal from the open-close detection unit 106 being connected to the robot controlling unit 102. When the operator enters the area within the safety protective fence 104 for operation while the robot 101 is in operation, the operator opens the safety protective fence door 105, an opening signal from the open-close detection unit 106 is outputted to the robot controlling unit 102, and the robot controlling unit 102 cuts off a power supply to a motor, not shown, which is provided on the robot 101 to stop the driving of the robot 101 and similarly stops the operation of the robot with a brake, not shown, and holds the posture of the robot 101.
When teaching the robot 101, by selecting a teaching mode by a control section 107 provided on a control panel of the robot controlling unit 102, the teaching unit 103 or an external input signal, not shown, the safety protective fence door 105 is opened, and even though the opening signal is being outputted from the open-close detection unit 106, by operating an enable switch, not shown, which is equipped on the teaching unit 103, the power supply to the motor is enabled. By operating a robot arm control key, not shown, which is provided on the teaching unit 103 in such a state that power is being supplied to the motor, the robot 102 is put into operation, and the addition of a teaching point or registration of a modification is made to an operation program which is an operation procedure for an operation that is carried out by the robot 101. When the teaching operation is completed, the operator gets out of the safety protective fence 104 and closes the safety protective fence door 105, whereupon a closure signal is outputted from the open-close detection unit 106 to the robot controlling unit 102. In this state, by selecting an automatic operation mode (also referred to as a repeat mode) by the control section 107, the teaching unit 103 or an external input signal, a power supply command to the motor can be received, and when a power supply command is inputted, power is supplied to the motor, and thereafter, by receiving an operation start command from the control section 107, the teaching unit 103 or an external input, a reproducing operation of the operation program is started.
In addition, in activating the operation program in the way described above, to prevent the operator from being exposed to a danger, the safety of the operator is required to be ensured by keeping him or her off the vicinity of the robot. To enhance the safety further, there has been proposed an idea in which a sensor is provided at the exit/entrance in the safety protective fence 104, so that the existence of the operator or an intruder is verified based on an output signal from the sensor (refer, for example, to Patent Document No. 1).    Patent Document No. 1: JP-A-5-50390